Spatial resolution of degradation in stabilized polystyrene and polypropylene plaques exposed to accelerated photodegradation or heat aging

Spatial resolution of photo and thermooxidation processes in polypropylene (PP) and polystyrene (PS) plaques was studied by electron spin resonance imaging (ESRI) and attenuated total reflectance Fourier-transform infrared spectroscopy (ATR FTIR). Polymer plaques made of PP and PS stabilized with various systems based on hindered amine stabilizers (HAS) were exposed to accelerated photodegradation and to heat aging in air atmosphere. Concentration profiles of nitroxides generated during the degradation process in the plaques were measured by ESRI, carbonyl and hydroxy groups were identified by ATR FTIR, transparency of the plaques in the actinic part of solar radiation, including a part of UV-B (295-315 nm), full range of UV-A (315-400 nm) and visible radiation was measured by optical techniques. A mechanism of the degradation consistent with all experimental data is suggested.